Telephone-receiver.



S. G. BROWN.

TELEPHONE RECEIVER.

APPLICATION FILED MAR.27,1911.

1,096,676. Patented May'12, 1914. v

ZflZ 51; e 6 5 66. 2720672707 Z5726 Q; Era -.0 W /J SIDNEY GEORGE BROWN,OF LONDON, ENGLAND. 1

TELEPHONE-RECEIVER Specification of Letters Patent.

. Patented May 12, 1914.

Application filed March 2? 1911. Serial No. 617,228.

To all whom it may concern:

' ticular reference to telephone receivers, the

Be it known that I, SIDNEY Gnonon BROWN, a subject of the King of GreatBritain, residing at 4 Great Winchester street, in the city and countyof London, England, have invented certain new and useful ImprovementsRelating to Telephone-Receivers, of which the following is aspecification.

This invention relates to. the reproduction of sound by electrical meansand has parchief object being to enable a high efiiciency of conversionof oscillations or variations of electric current into acousticvibrations to be obtained.

The usual telephone receiver consistsrof a polarized electromagnetthrough the coil of which the line currents pass, and a soft irondiaphragm ripped peripherally and thereby held a short distance awayfrom the electromagnet. Variations in the strength of the line currentcause the diaphragm to vibrate, and, in so doing, to set the surroundinair into vibration. The responsiveness o the diaphragm as usuallyemployed and the transmission of its vibrations to the air are imperfectfor several reasons. In the first place owing to the peripheral grippinof the diaphragm it cannot vibrate uni ormly at all points on itssurfaceyalso owing to the diaphragm serving to complete the magneticcircuit of the electromagnet, its thickness is considerable; and, owingto this, thickness of the diaphragm and to its being composed of iron,it is comparatively heavy with the result that its inertia makes itsluggish in ac 7 tion. Moreover in regard to the transmission of thevibrations through the air, sufficient attention has not been paid tothe volume of air set in motion and the variations of air pressure forproducing the most effective transmission. The dimensions of theear-drum and of the aural cavity may be taken as invariable factors insuch considerations. Now these factors being known, there are certainrelations existing between them and the size of the diaphragm, thenature of the air pressure variations, and the volume of air set inmotion for the most effective reproduction of the sounds, and thetransmission of them to the ear-drum.

The telephone receiver constructed in accordance with the presentinvention is designed to eliminate the causes of inefficiency abovereferred to.

According to this invention the diaphragm of the receiver is madeextremely light but is so shaped that notwithstanding its extremelightness it is-comparatively rigid. I have found that a diaphragm ofaluminium formed conically from a very thin disk of that metal and ifnecessary suitably stiffened by ribs, or corrugations, or" otherwise,possesses the requisite properties to a satisfactory degree. The thindisk of aluminium may conveniently be spun into a conical shape with aHat center piece.

It is advantageous for the strength to be greatest at the center andprogresslvely less toward the edge, and by starting the spinningoperation at the edge and working toward the center, this property ofthe spun disk will be naturally produced owing to the graduatedthickness of the disk. To increase this effect resort may be made to theknown expedient of assembling several disks of different diameter into apile. The thickness of such disks may be of the order of 21} thousandthsof an inch. Some idea as to the lightness of a diaphragm so formed maybe. gained from the fact that when itis v allowed to drop to the groundit does not fall like a heavy mass of metal, but moves gently throughthe air. The mere conical shape of the diaphragm. will insure. aconsiderable amount of rigidity but this may be increased by providingradial ribs or' corrugations on it. This diaphragm is mounted upon aresilient member which responds to the variations of line current; thesaid resilient member may consist of a metal strip or reed away portion,its own control and that of the diaphragm. The diaphragm ispreferablyattached at its center to a point on the metal strip or reedslightly eccentric with respect to the axis of the coil through whichthe line currents pass. The diaphragm is so arranged as to be free tomove as a whole, that is to say all points on its surface vibrateequally, and to insure this action the periphery of the diaphragm iseither quite' free or is attached to the usual casing by a mere thinring of flexible material. The in her face of-the cover or ear-piece ofthe receiver is shaped to conform approximately rzontainrng'wvithinitself, by reason of a cutto the shape of the diaphragm, and is situatedat a comparatively short distance from this diaphragm, thereby avoidingan undue amount of space between the diaphragm and reference to theaccompanying drawings, in

the cover or ear-piece. In order'that the inventionmay be clearlyunderstood and readily carried into efiect I will now describe the samemore fully with which:

Figure 1 is a plan with the cover removed, and Fig-.2 a sectionalelevation, of one constructional form of my improved receiver. Thesedrawings represent a full size receiver, and the more importantdimensions such as the diameter of the diaphragm, the

extent of its eccentricity, and the volume- I of larger size ispreferable. Fig. 3 is adetail view of a diaphragmbuilt up'of severaldiaphragms of difi'erent diameter.

. A is. the casing and B the ear piece or cover of the receiver.

G represents the coil and]) the core of a polarized electromagnet ofwhich 'N and S are the north and south polesdespectively.

; E is a metal reed one end of which is held down upon a bridge piece Eby two adjusting screws E the free end of on the casing E this reedextends over the core D of the electaro-magnet. A portion E of this reedis cut away to increase its'fiexibility and decrease its weight. Ihavefound that. a suitable free period -forthe reed is from eight hundred toone thousand. The extent to which the reed E can approach the core D maybe regulated by packing some layers of paper between these parts or byarranging a set screw to make'contact with the reed.

F is a light aluminium diaphragm of conical'form. It is attached at itscenter to the reed E at a point eccentric with respect to.

the axis of the core I), the eccentricity being toward the fixed end ofthe reed. Although 'I have shown the best position for attaching thediaphragm in the particular receiver illustrated, the best position'onany reed can vbe foundby experiment by 'means of a stethoscope 'and byexploring the reed withthe aid of a movable diaphragm. I

The diaphragm F iswflexibly attached at its periphery by a ring F" oftissue paper or other suitable material that will not exert appreciablerestraint upon the diaphragm,

' to a removable flange on the casing A. ThlS ring F may be attached tothe diaphragm and to the aforesaid flange by adhesive.

L reed E It will understood that owing'to the extreme lightness ofthediaphragm and to its freedom from peripheral constraint, it will behighly responsive to movements of the reed E and will vibrate as awhole. It will also be observed that the function of the is not to setthe air in motion, but

only to carry the diaphragm and control its movement. self, by reason ofits cut away portion E, the means of its own control and that of thediaphragm, and also serves to complete the This reed contains, withinit-- magnetic circuit;the diaphragm forms no part of this circuit. Theinner face of the piece B conforms approxi matelyv to the shape of-thediaphragm and I its distance from the diaphragm is such as to give onlythe requisite air space between these two parts: The sectional area ofthe central hole or holes in' the ear-piece is suitably proportioned tothe aforesaid air space.

Although the invention has been described and illustrated with referenceto'a watch type of receiver, it is of'course equally ap-,

plicable to the long-handle type of receiver.

What I claim and desire to secure by Letters Patent of the United Statesis:-

1. In a telephone receiver, a coil-through which the linecurrentsipass', a. resilient metal reed responsive to variations ofcurrent in the coil, and having an intermediate cut-away portion toimpart inherent flexibil-.

ity, alight rigid peripherally unrestrained conical diaphragm'carried byits center .on

said'reed, and an ear piece situated over the diaphragm. y r

2. In a telephone receiver, a polarized electromagnet, a coil throughwhich the line i currents pass, a resilient metal reed responsive tovariations of current'in the coil and having an intermediate cut-awayportionto impart inherent flexibility, a light peripherally unrestrainedconical diaphragm cari 5d.

by its center-on said good, and an ear piece.

situated over the diaphragm.

, 3. In a telephone receiver, apolarized electromagnet, a coil throughwhich the line currents pass, a resilient member responsive tovariations of current in the 0011, a hght peripherally unrestrainedconical diaphragm carried by its center ,on said member. eccentricallywith respect to the electromagnet andv an ear piece situated over-"thediaphragm.

4:. Ina telephone receiver, a polarized electromagnet, a coil throughwhich the line currents pass, a resilient metal reed serving aselectromagnet armature and having an intermediate cut-away, portionto'impart inherentflexibility, a' peripherallyv unre strained conicaldiaphragm by 'its center on the free end of the-said armature, and anear piece situated over the diaphragm. I

5. In a telephone receiver, a coil through which the line currents pass,a resilient metal reed responsive to variations of current in the'coiland having an, intermediate cutaway portion to impart inherentflexibility,

.a light peripherally unrestrained conical diaphragm carried by itscenter on said ree and an earpiece the inner face of which conformsapproximately to the com ical shape of the-diaphragm.

6. In atelephone receiver, a casing, a po larized electromagnct attachedto the back "of the casing, a coil through which the line currents pass,a resilient metal reed responsive to variations of current in the coiland having an intermediate cut-away ortion to impart inherentflexibility, a lig t conical diaphragm carried by its center on saidreed with its apex pointing toward the back of the casing, and a coveror ear-piece with a conical inner face conforming approximately to thatof the diaphragm.

7. In a telephone recelver, a diaphragm comprising a conically shapedsheet of metal spun aluminium diaphragm thickest at the center andprogressively thinner toward the periphery, and a resilient member forcarrying said diaphragm by its center.

8. In a telephone receiver a conically thickest at the center andprogressively thinner toward the periphery, and a resilient member forcarrying said diaphragm by its center.

9. In a telephonereceiver, a diaphra comprising a sheet of metal havinga 5: 1 centerpiece and a conical flange portion the thickness of whichdecreases progressively toward the periphery, and a resilient memher forcarrying said diaphragm by its center.

10. In a telephone receiver, an aluminium diaphragm comprising a flatcenterpiece and a conically spun flange portion the thickness of whichdecreases progressively toward the periphery, and a resilient membersupporting the diaphragm by its center. I

11. In a telephone receiver, a casing, a

coil through which the line currents .pass, a resilient memberresponsive to variations of current in the coil, a light conicaldiaphragm carried by its center on said member, an ear piece situatedover the diaphragm, and a flexible ring of material connecting theperiphery of the diaphragm to the casing, said material being so thinand light as to exert no appreciable restraint upon the diaphragm.

12. In a, telephone receiver, a casing, re-

SIDNEY GEORGE BROWN.

Witnesses:

W. HENRY I'IARVE'I, W. J. SKER'I'EN.

